~3-nm ZnO Nanoislands Deposition and Application in Charge Trapping Memory Grown by Single ALD Step

Abstract

Low-dimensional semiconductor nanostructures are of great interest in high performance electronic and photonic devices. ZnO is considered to be a multifunctional material due to its unique properties with potential in various applications. In this work, 3-nm ZnO nanoislands are deposited by Atomic Layer Deposition (ALD) and the electronic properties are characterized by UV-Vis-NIR Spectrophotometer and X-ray Photoelectron Spectroscopy. The results show that the nanostructures show quantum confinement effects in 1D. Moreover, Metal-Oxide-Semiconductor Capacitor (MOSCAP) charge trapping memory devices with ZnO nanoislands charge storage layer are fabricated by a single ALD step and their performances are analyzed. The devices showed a large memory window at low operating voltages with excellent retention and endurance characteristics due to the additional oxygen vacancies in the nanoislands and the deep barrier for the trapped holes due to the reduction in ZnO electron affinity. The results show that the ZnO nanoislands are promising in future low power memory applications.

Nanoislands-Based Charge Trapping Memory: A Scalability Study

“…The latter is limited by the quiescent bias state of the device which keeps the Silicon surface in depletion. During the retention operation, without an applied gate bias, the band alignment is unfavorable for tunneling, thus, the nano-islands based memory has a long retention time as already proven in our previous works [9][10].…”

“…High frequency C-V characteristic of the memory a) with ZrO2 islands b) with ZnO islands. Reused with permission from [9][10] width of 20-nm and 10-nm, respectively. The following tables I and II summarize the obtained results for the 32-nm technology (100-nm physical gate length) and our fabricated devices results with ZnO and ZrO 2 nanoislands, respectively.…”

“…One point that can cause reliability issues is the quantum confinement effects (QCE) in the nano-islands. In fact, we have already demonstrated that ZnO showed QCE in 1D while no such effects are obtained in the ZrO 2 islands [9][10]. Therefore, with ZnO, the performance of the memory cells will be different based on the different sizes of the islands embedded within each cell since their electronic properties will vary due to the QCE [14][15][16][17].…”

“…Two nano-island materials are studied for the charge trapping layer: ZnO and ZrO 2 which are deposited by 20 cycles of the atomic layer deposition (ALD) process. More details about the fabrication of the memory and the growth of the nano-islands are explained in our recent papers [9][10]. Using an atomic force microscope, the distribution and topography of the nanoislands are extracted.…”

“…ZnO [5][6] and ZrO 2 [7][8] have shown great potential in several applications including memory devices. In this paper, a scalability study is conducted on ZnO and ZrO 2 nano-islands based memory devices that have been recently demonstrated by our group [9][10].…”